Flash User Page

 

The bootloader uses the flash User page is used to store the I/O conditions that determine which of the USB DFU ISP and the application to start at the end of the boot process.

 

Bits of the Flash User Page

Name

Description

7:0

ISP_CRC8

CRC8 on the bootloader User page configuration word with polynomial:

P(X) = X^8+X^2+X+1.

This CRC is used to check the validity of this configuration word.

Wizard compute this value

15:8

ISP_IO_COND_PIN

The GPIO pin number to test during the boot process to know which of the USB DFU ISP and the application to start.

The wizard will give possible values are depending on 1st page selection:

-          GPIO from 0 to 109 for AT32UC3A QFP144

-          GPIO from 0 to 69 for AT32UC3A QFP100

-          GPIO from 0 to 43 for AT32UC3B QFP64

-          GPIO from 0 to 27 for AT32UC3B QFP48

16

ISP_IO_COND_LEVEL

Active level of ISP_IO_COND_PIN that the bootloader will consider as a request for starting the USB DFU ISP:

-          0 for GPIO low level

-          1 for GPIO high level

31:17

ISP_BOOT_KEY

Boot key = 494Fh. This key is used to identify the word as meaningful for the bootloader.